Disc Brake Conversion Recommendation

Discussion in 'The whoa and the sway.' started by 1968_GS400, Sep 18, 2021.

  1. 69GS430/TKX

    69GS430/TKX Silver Level contributor

    I am glad this topic came up because I, too, need help deciding which kit to buy for my '69 GS400 that will be wearing 15-inch wheels. I only want to convert the fronts to disc right now. And my car is a NON-power car, so no booster. The questions I need help with are:

    1. Are these kits intended to only be used with a booster, or will they work on a system that has a non-PB master cylinder?
    2. If I can install disc brakes on the front while keeping it non-power, will I be able to stop the car? Or will it require so much pedal strength that only Lou Ferrigno would be strong enough?
    3. Would going with 2-piston calipers lessen the leg strength required to stop the car?

    Thanks guys.
    1968_GS400 likes this.
  2. Oldskewl59

    Oldskewl59 Silver Level contributor

    I think there are different master cylinders for each application. It has to do with the diameter of the "piston" that drives the fluid. Also, a disc reservoir needs (or uses) more fluid than a drum. Some Corvettes had 4 wheel disc manual brakes. I saw a pretty good explanation on this at Baer Brakes talking about their master cylinders. In your case you will need to change the master cylinder and if you put disc brakes on the back at a later time probably change it again. GM master cylinders are cheap and I believe they all have a common GM mount.
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  3. 1968_GS400

    1968_GS400 Founders Club Member

    Here are the Right Stuff manual kits for the 69

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  4. Ken Mild

    Ken Mild King of 18 Year Resto's

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  5. 1968_GS400

    1968_GS400 Founders Club Member

    Jeff said he had 15" wheels.

    Based on what I discussed with Right Stuff, I think all those at that link for the 69 above are for 15" factory drum brake wheels or larger. If it says "Fits factory 14"" or larger disc brake wheels" it doesn't mean "14" or larger factory drum brake wheels.” That is what threw me off before.

    I think this is the only kit they have for manual disc brakes for 14" wheels:

    Last edited: Sep 28, 2021
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  6. 69GS430/TKX

    69GS430/TKX Silver Level contributor

    Thanks for that info. I do recall that my '67 Vette had non-power brakes and they worked pretty good.
    Glad to know that even though I will need a new master cylinder, it won't cost me too much.
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  7. 69GS430/TKX

    69GS430/TKX Silver Level contributor

    Correct, I am now running 15- inch Rallye wheels that probably came off a 1970s car. I want a little more ground clearance so my headers won't scrape on speed bumps. :)

    Thanks. I guess that's the kind of kit I will be needing. Am I correct in assuming that 15" Rallye wheels are "disc brake wheels" ?
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  8. 69GS430/TKX

    69GS430/TKX Silver Level contributor

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  9. 1968_GS400

    1968_GS400 Founders Club Member

    To be honest, I am not sure what “disc brake wheel” means exactly other than there has to be enough room for the calipers. I guess if those rallye wheels came off of a car with disc brakes they’d be “disc brake wheels.”

    I think you will have less problems with the 15” rallye wheels than with the 14” rallye wheels I have.

    You should be able to use any of the 15” manual disc brake kits and don’t have to use the 14” kits.

    I may be mistaken but I think you can use that OPGI kit but need to get the correct master cylinder and disc/drum proportioning valve for manual front disc brakes/manual rear drum brakes.
    Last edited: Sep 29, 2021
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  10. 69GS430/TKX

    69GS430/TKX Silver Level contributor

    That is encouraging! I plan to ask the OPGI experts about this possibility tomorrow during their office hours. I will post their answer in case it might help anyone else here who could use the info.
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  11. 69GS430/TKX

    69GS430/TKX Silver Level contributor

    OPGI Update: Their tech line is down, but I did find the following questions already answered by them about this particular kit:

    Q: My 66 el camino is manual brakes will the single chamber master cylinder work?
    A: Yes, this kit would work with your current set up. Thanks for the question.

    Q: What size brake pad does this require for future replacement?
    A: This kit uses a D52 caliper, pads can be found locally.

    Q: Was wondering why you have to use 15in or larger wheels on your disc breaks conversion kits? I have a 66 GTO and I have 14in on the front w/15in in the rear. And I have had disc on the front for over twenty years. So I'm curious what suppose to happen or go wrong?
    A: Thank you for the inquiry. Please contact our Technical Support department for immediate assistance toll free at 800-243-8355, and select option 3.
  12. 1968_GS400

    1968_GS400 Founders Club Member

    I think you will need a 1-inch bore master cylinder and the disc/drum proportioning valve. I can't find the master cylinder on the OPGI website for a manual brake system, but I think this is the upper kit from Right Stuff, although not sure if it's a good idea to mix brands or not.


    You can look at the components tab and see the parts that it comes with.

    I think this is the comparable full upper/lower manual kit from Right Stuff


    This video starting at around 1:50 has some information about manual brake master cylinders:

    This video is also interesting

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  13. 69GS430/TKX

    69GS430/TKX Silver Level contributor

    Great info, thanks! I will check it out, and the videos.
  14. 1968_GS400

    1968_GS400 Founders Club Member

    Did you end up getting the OPGI kit?

    I bought the 14” kit from Right Stuff because it showed as in stock, but they weren’t in stock after all. They are still waiting on brackets. Their new ETA is middle of November because of supply chain issues.
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  15. 1969BSGS

    1969BSGS Active Member

    I bought a used Wilwood Part # 140-10996 Dynalite Front Brake kit for my 69 Skylark, It works with disc or drum spindles and I'm pretty sure it will work with 14 inch wheels also, Pretty amazing how light the rotors & calipers are....
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  16. 69GS430/TKX

    69GS430/TKX Silver Level contributor

    I had it in my Shopping Cart, but when I saw what the shipping cost would be, I chickened out. Guess I will wait and see what the future holds. Who needs good brakes, anyhow? Our motto is "Go Fast With Class," not "Stop Within a Reasonable Distance." :)
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  17. 69GS430/TKX

    69GS430/TKX Silver Level contributor

    I really like the idea of a Wilwood system for my '69. Does that guy have another one for sale? :)
  18. 1968_GS400

    1968_GS400 Founders Club Member

    Lol. They have free shipping but for some reason that part is excluded from free shipping

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  19. 69GS430/TKX

    69GS430/TKX Silver Level contributor

    I suspected it was too good a sale to be true!

    Item: Regularly $200, now $100
    Shipping: Was free, now $100

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